| 1 | /* SPDX-License-Identifier: GPL-2.0
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| 2 | *
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| 3 | * Copyright (C) 1999, 2000, 2002 Niibe Yutaka
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| 4 | * Copyright (C) 2003 - 2008 Paul Mundt
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| 5 | */
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| 6 |
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| 7 | ! NOTE:
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| 8 | ! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
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| 9 | ! to be jumped is too far, but it causes illegal slot exception.
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| 10 |
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| 11 | /*
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| 12 | * entry.S contains the system-call and fault low-level handling routines.
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| 13 | * This also contains the timer-interrupt handler, as well as all interrupts
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| 14 | * and faults that can result in a task-switch.
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| 15 | *
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| 16 | * NOTE: This code handles signal-recognition, which happens every time
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| 17 | * after a timer-interrupt and after each system call.
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| 18 | *
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| 19 | * NOTE: This code uses a convention that instructions in the delay slot
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| 20 | * of a transfer-control instruction are indented by an extra space, thus:
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| 21 | *
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| 22 | * jmp @k0 ! control-transfer instruction
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| 23 | * ldc k1, ssr ! delay slot
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| 24 | *
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| 25 | * Stack layout in 'ret_from_syscall':
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| 26 | * ptrace needs to have all regs on the stack.
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| 27 | * if the order here is changed, it needs to be
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| 28 | * updated in ptrace.c and ptrace.h
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| 29 | *
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| 30 | * r0
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| 31 | * ...
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| 32 | * r15 = stack pointer
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| 33 | * spc
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| 34 | * pr
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| 35 | * ssr
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| 36 | * gbr
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| 37 | * mach
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| 38 | * macl
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| 39 | * syscall |
| 40 | *
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| 41 | */
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| 42 | |
| 43 |
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| 44 | |
| 45 | |
| 46 | |
| 47 | |
| 48 | |
| 49 | |
| 50 |
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| 51 |
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| 52 | .align 2
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| 53 | ENTRY(exception_error)
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| 54 | !
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| 55 | TRACE_IRQS_ON
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| 56 | sti
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| 57 | mov.l 1f, r0
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| 58 | jmp @r0
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| 59 | nop
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| 60 |
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| 61 | .align 2
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| 62 | 1: .long do_exception_error
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| 63 |
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| 64 | .align 2
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| 65 | ret_from_exception:
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| 66 | CFI_STARTPROC simple
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| 67 | CFI_DEF_CFA r14, 0
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| 68 | CFI_REL_OFFSET 17, 64
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| 69 | CFI_REL_OFFSET 15, 60
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| 70 | CFI_REL_OFFSET 14, 56
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| 71 | CFI_REL_OFFSET 13, 52
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| 72 | CFI_REL_OFFSET 12, 48
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| 73 | CFI_REL_OFFSET 11, 44
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| 74 | CFI_REL_OFFSET 10, 40
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| 75 | CFI_REL_OFFSET 9, 36
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| 76 | CFI_REL_OFFSET 8, 32
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| 77 | preempt_stop()
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| 78 | ENTRY(ret_from_irq)
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| 79 | !
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| 80 | mov |
| 81 | mov.l @(r0,r15), r0 ! get status register
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| 82 | shll r0
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| 83 | shll r0 ! kernel space?
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| 84 | get_current_thread_info r8, r0
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| 85 | bt resume_kernel ! Yes, it's from kernel, go back soon
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| 86 |
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| 87 | #ifdef CONFIG_PREEMPTION
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| 88 | bra resume_userspace
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| 89 | nop
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| 90 | ENTRY(resume_kernel)
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| 91 | cli
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| 92 | TRACE_IRQS_OFF
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| 93 | mov.l @(TI_PRE_COUNT,r8), r0 ! current_thread_info->preempt_count
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| 94 | tst r0, r0
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| 95 | bf noresched
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| 96 | need_resched:
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| 97 | mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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| 98 | tst #_TIF_NEED_RESCHED, r0 ! need_resched set?
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| 99 | bt noresched
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| 100 |
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| 101 | mov #OFF_SR, r0
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| 102 | mov.l @(r0,r15), r0 ! get status register
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| 103 | shlr r0
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| 104 | and #(0xf0>>1), r0 ! interrupts off (exception path)?
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| 105 | cmp/eq #(0xf0>>1), r0
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| 106 | bt noresched
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| 107 | mov.l 1f, r0
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| 108 | jsr @r0 ! call preempt_schedule_irq
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| 109 | nop
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| 110 | bra need_resched
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| 111 | nop
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| 112 |
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| 113 | noresched:
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| 114 | bra __restore_all
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| 115 | nop
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| 116 |
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| 117 | .align 2
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| 118 | 1: .long preempt_schedule_irq
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| 119 | #endif
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| 120 |
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| 121 | ENTRY(resume_userspace)
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| 122 | ! r8: current_thread_info
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| 123 | cli
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| 124 | TRACE_IRQS_OFF
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| 125 | mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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| 126 | tst #(_TIF_WORK_MASK & 0xff), r0
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| 127 | bt/s __restore_all
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| 128 | tst #_TIF_NEED_RESCHED, r0
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| 129 |
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| 130 | .align 2
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| 131 | work_pending:
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| 132 | ! r0: current_thread_info->flags
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| 133 | ! r8: current_thread_info
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| 134 | ! t: result of "tst #_TIF_NEED_RESCHED, r0"
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| 135 | bf/s work_resched
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| 136 | tst #(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME), r0
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| 137 | work_notifysig:
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| 138 | bt/s __restore_all
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| 139 | mov r15, r4
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| 140 | mov r12, r5 ! set arg1(save_r0)
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| 141 | mov r0, r6
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| 142 | sti
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| 143 | mov.l 2f, r1
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| 144 | mov.l 3f, r0
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| 145 | jmp @r1
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| 146 | lds r0, pr
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| 147 | work_resched:
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| 148 | mov.l 1f, r1
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| 149 | jsr @r1 ! schedule
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| 150 | nop
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| 151 | cli
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| 152 | TRACE_IRQS_OFF
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| 153 | !
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| 154 | mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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| 155 | tst #(_TIF_WORK_MASK & 0xff), r0
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| 156 | bt __restore_all
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| 157 | bra work_pending
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| 158 | tst #_TIF_NEED_RESCHED, r0
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| 159 |
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| 160 | .align 2
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| 161 | 1: .long schedule
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| 162 | 2: .long do_notify_resume
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| 163 | 3: .long resume_userspace
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| 164 |
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| 165 | .align 2
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| 166 | syscall_exit_work:
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| 167 | ! r0: current_thread_info->flags
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| 168 | ! r8: current_thread_info
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| 169 | tst #(_TIF_WORK_SYSCALL_MASK & 0xff), r0
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| 170 | bt/s work_pending
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| 171 | tst #_TIF_NEED_RESCHED, r0
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| 172 | TRACE_IRQS_ON
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| 173 | sti
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| 174 | mov r15, r4
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| 175 | mov.l 8f, r0 ! do_syscall_trace_leave
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| 176 | jsr @r0
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| 177 | nop
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| 178 | bra resume_userspace
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| 179 | nop
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| 180 |
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| 181 | __restore_all:
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| 182 | mov #OFF_SR, r0
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| 183 | mov.l @(r0,r15), r0 ! get status register
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| 184 |
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| 185 | shlr2 r0
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| 186 | and #0x3c, r0
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| 187 | cmp/eq #0x3c, r0
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| 188 | bt 1f
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| 189 | TRACE_IRQS_ON
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| 190 | bra 2f
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| 191 | nop
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| 192 | 1:
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| 193 | TRACE_IRQS_OFF
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| 194 | 2:
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| 195 | mov.l 3f, r0
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| 196 | jmp @r0
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| 197 | nop
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| 198 |
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| 199 | .align 2
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| 200 | 3: .long restore_all
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| 201 |
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| 202 | .align 2
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| 203 | syscall_badsys: ! Bad syscall number
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| 204 | get_current_thread_info r8, r0
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| 205 | mov #-ENOSYS, r0
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| 206 | bra resume_userspace
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| 207 | mov.l r0, @(OFF_R0,r15) ! Return value
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| 208 |
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| 209 | /*
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| 210 | * The main debug trap handler.
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| 211 | *
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| 212 | * r8=TRA (not the trap number!)
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| 213 | *
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| 214 | * Note: This assumes that the trapa value is left in its original
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| 215 | * form (without the shlr2 shift) so the calculation for the jump
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| 216 | * call table offset remains a simple in place mask.
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| 217 | */
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| 218 | debug_trap:
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| 219 | mov r8, r0
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| 220 | and #(0xf << 2), r0
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| 221 | mov.l 1f, r8
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| 222 | add r0, r8
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| 223 | mov.l @r8, r8
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| 224 | jsr @r8
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| 225 | nop
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| 226 | bra ret_from_exception
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| 227 | nop
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| 228 | CFI_ENDPROC
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| 229 |
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| 230 | .align 2
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| 231 | 1: .long debug_trap_table
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| 232 |
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| 233 | /*
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| 234 | * Syscall interface:
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| 235 | *
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| 236 | * Syscall #: R3
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| 237 | * Arguments #0 to #3: R4--R7
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| 238 | * Arguments #4 to #6: R0, R1, R2
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| 239 | * TRA: See following table.
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| 240 | *
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| 241 | * (TRA>>2) Purpose
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| 242 | * -------- -------
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| 243 | * 0x00-0x0f original SH-3/4 syscall ABI (not in general use).
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| 244 | * 0x10-0x1f general SH-3/4 syscall ABI.
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| 245 | * 0x1f unified SH-2/3/4 syscall ABI (preferred).
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| 246 | * 0x20-0x2f original SH-2 syscall ABI.
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| 247 | * 0x30-0x3f debug traps used by the kernel.
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| 248 | * 0x40-0xff Not supported by all parts, so left unhandled.
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| 249 | *
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| 250 | * For making system calls, any trap number in the range for the
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| 251 | * given cpu model may be used, but the unified trap number 0x1f is
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| 252 | * preferred for compatibility with all models.
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| 253 | *
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| 254 | * The low bits of the trap number were once documented as matching
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| 255 | * the number of arguments, but they were never actually used as such
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| 256 | * by the kernel. SH-2 originally used its own separate trap range
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| 257 | * because several hardware exceptions fell in the range used for the
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| 258 | * SH-3/4 syscall ABI.
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| 259 | *
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| 260 | * This code also handles delegating other traps to the BIOS/gdb stub.
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| 261 | *
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| 262 | * Note: When we're first called, the TRA value must be shifted
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| 263 | * right 2 bits in order to get the value that was used as the "trapa"
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| 264 | * argument.
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| 265 | */
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| 266 |
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| 267 | .align 2
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| 268 | .globl ret_from_fork
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| 269 | ret_from_fork:
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| 270 | mov.l 1f, r8
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| 271 | jsr @r8
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| 272 | mov r0, r4
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| 273 | bra syscall_exit
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| 274 | nop
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| 275 |
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| 276 | .align 2
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| 277 | .globl ret_from_kernel_thread
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| 278 | ret_from_kernel_thread:
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| 279 | mov.l 1f, r8
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| 280 | jsr @r8
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| 281 | mov r0, r4
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| 282 | mov.l @(OFF_R5,r15), r5 ! fn
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| 283 | jsr @r5
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| 284 | mov.l @(OFF_R4,r15), r4 ! arg
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| 285 | bra syscall_exit
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| 286 | nop
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| 287 |
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| 288 | .align 2
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| 289 | 1: .long schedule_tail
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| 290 |
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| 291 | /*
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| 292 | * The poorly named main trapa decode and dispatch routine, for
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| 293 | * system calls and debug traps through their respective jump tables.
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| 294 | */
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| 295 | ENTRY(system_call)
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| 296 | setup_frame_reg
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| 297 | |
| 298 | mov.l 1f, r9
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| 299 | mov.l @r9, r8 ! Read from TRA (Trap Address) Register
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| 300 | |
| 301 |
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| 302 | mov |
| 303 | add r15, r10
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| 304 | mov.l r8, @r10 ! set TRA value to tra
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| 305 |
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| 306 | /*
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| 307 | * Check the trap type
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| 308 | */
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| 309 | mov |
| 310 | cmp/hi r9, r8
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| 311 | bt/s debug_trap ! it's a debug trap..
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| 312 | nop
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| 313 |
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| 314 | TRACE_IRQS_ON
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| 315 | sti
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| 316 |
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| 317 | !
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| 318 | get_current_thread_info r8, r10
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| 319 | mov.l @(TI_FLAGS,r8), r8
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| 320 | mov #(_TIF_WORK_SYSCALL_MASK & 0xff), r10
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| 321 | mov #(_TIF_WORK_SYSCALL_MASK >> 8), r9
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| 322 | tst r10, r8
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| 323 | shll8 r9
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| 324 | bf syscall_trace_entry
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| 325 | tst r9, r8
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| 326 | bf syscall_trace_entry
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| 327 | !
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| 328 | mov.l 6f, r8 ! Number of syscalls
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| 329 | cmp/hs r8, r3
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| 330 | bt syscall_badsys
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| 331 | !
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| 332 | syscall_call:
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| 333 | shll2 r3 ! x4
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| 334 | mov.l 3f, r8 ! Load the address of sys_call_table
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| 335 | add r8, r3
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| 336 | mov.l @r3, r8
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| 337 | mov.l @(OFF_R2,r15), r2
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| 338 | mov.l @(OFF_R1,r15), r1
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| 339 | mov.l @(OFF_R0,r15), r0
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| 340 | mov.l r2, @-r15
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| 341 | mov.l r1, @-r15
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| 342 | mov.l r0, @-r15
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| 343 | jsr @r8 ! jump to specific syscall handler
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| 344 | nop
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| 345 | add #12, r15
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| 346 | mov.l @(OFF_R0,r15), r12 ! save r0
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| 347 | mov.l r0, @(OFF_R0,r15) ! save the return value
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| 348 | !
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| 349 | syscall_exit:
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| 350 | cli
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| 351 | TRACE_IRQS_OFF
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| 352 | !
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| 353 | get_current_thread_info r8, r0
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| 354 | mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
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| 355 | tst #(_TIF_ALLWORK_MASK & 0xff), r0
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| 356 | mov #(_TIF_ALLWORK_MASK >> 8), r1
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| 357 | bf syscall_exit_work
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| 358 | shlr8 r0
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| 359 | tst r0, r1
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| 360 | bf syscall_exit_work
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| 361 | bra __restore_all
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| 362 | nop
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| 363 |
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| 364 | .align 2
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| 365 | syscall_trace_entry:
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| 366 | ! Yes it is traced.
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| 367 | mov r15, r4
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| 368 | mov.l 7f, r11 ! Call do_syscall_trace_enter which notifies
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| 369 | jsr @r11 ! superior (will chomp R[0-7])
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| 370 | nop
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| 371 | cmp/eq #-1, r0
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| 372 | bt syscall_exit
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| 373 | ! Reload R0-R4 from kernel stack, where the
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| 374 | ! parent may have modified them using
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| 375 | ! ptrace(POKEUSR). (Note that R0-R2 are
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| 376 | ! reloaded from the kernel stack by syscall_call
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| 377 | ! below, so don't need to be reloaded here.)
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| 378 | ! This allows the parent to rewrite system calls
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| 379 | ! and args on the fly.
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| 380 | mov.l @(OFF_R4,r15), r4 ! arg0
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| 381 | mov.l @(OFF_R5,r15), r5
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| 382 | mov.l @(OFF_R6,r15), r6
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| 383 | mov.l @(OFF_R7,r15), r7 ! arg3
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| 384 | mov.l @(OFF_R3,r15), r3 ! syscall_nr
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| 385 | !
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| 386 | mov.l 6f, r10 ! Number of syscalls
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| 387 | cmp/hs r10, r3
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| 388 | bf syscall_call
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| 389 | mov |
| 390 | bra syscall_exit
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| 391 | mov.l r0, @(OFF_R0,r15) ! Return value
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| 392 |
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| 393 | .align 2
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| 394 | |
| 395 | 1: .long TRA
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| 396 | |
| 397 | 6: .long NR_syscalls
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| 398 | 3: .long sys_call_table
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| 399 | 7: .long do_syscall_trace_enter
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| 400 | 8: .long do_syscall_trace_leave
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